1. Field of the Invention
The present invention relates generally to a press plate of wire bond checking system and more particularly to a press plate mounted with a probe of wire bond checking system.
2. Description of the Related Art
In recent years, as the function of IC becomes complicated, there exists a need in the development of packing for an improved high density lead frame. BGA (Ball Grid Array) packages of the electronic and computer industries have been required to support higher lead counts within the same package footprint area. Lift bond or missing wire or bonding pad polluted with compound results in an open loop of the BGA package that causes the BGA package to fail to work. Conventional wire bonding systems, without checking wire bonding, cannot stop bonding immediately and open loops occur during wire bonding. So the wire bond system still continues to use unnecessary wire bonds that increase the cost of product.
U.S. Pat. No. 5,712,570, issued on Jan. 27, 1998 to Heo et al., discloses method for checking wire bond of a semiconductor package. An electroconductive metal layer of gold or copper is grounded on a chip-bonding portion of a PCB (Printed Circuit Board) of the BGA package as well as on a passage extending between the chip bonding-portion and the mold gate of the PCB. After a wire bonding-step, a probe and capillary of a wire bond checking system contact the mold gate and a semiconductor chip, respectively. Then, a current is sent to the BGA package from the checking system to check whether the wire bond is closed or not. When there is neither a lift bond nor a missing wire in BGA package, the wire will send the current. However, the probe of the wire bond checking system damages the mold gate and the semiconductor chip and presses to form a hole in the mold gate during wire bond checking. In addition, substrate of some BGA packages are designed without mold gates, such as the Viper BGA, Micro-Laminate BGA and so on. The wire bond checking system of U.S. Pat. No. 5,712,570 cannot apply to these substrates.
The present invention intends to provide a press plate mounting with a probe in the wire bond checking system. The probe is elastically attached to the press plate and contacts the inner fingers of the substrate during wire bond checking in such a way as to mitigate and overcome the above problem.
The primary objective of this invention is to provide a press plate of wire bond checking system which includes a press plate with a probe contacting the inner fingers of the substrate during wire bond checking.
The secondary objective of this invention is to provide a press plate of wire bond checking system which includes a probe that is elastically attached to the press plate to reduce damage to the substrate.
The present invention is a press plate of wire bond checking system in accordance with an embodiment; the press plate mainly includes a plate and a probe. The plate has an opening which corresponds to a chip of the substrate and inner finger thereof, and the probe is elastically attached to the edge of the opening for wire bond checking. After the wire bonding process, the wire connecting the chip and the inner finger of the substrate and the probe of the wire bond checking system form a loop. Then a current is sent to the substrate from the wire bond checking system to check for the wire lift bond or missing wire. When the wire bond checking system finds lift bond or missing wire, the wire bonding process stops immediately to avoid unnecessary wire bonding.
Other objectives, advantages and novel features of the invention will become more apparent from the following detailed description and the accompanying drawings.